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Battery issue again

PamJ

New Member
Can anyone provide me with an idiots guide to MP batteries please.
We had a new leisure battery last year after the existing one exploded emitting smoke and gases while driving it, not a pleasant experience!
After another period of the MP standing still because of Covid restrictions etc went to charge the engine battery but now know I attached charger to the relay under the bonnet for a few hours, as I mistook it for the battery. Possibly linked to this the new leisure battery started to smoke and give off fumes the same as last time.
I can’t find where the engine battery is or it’s charging points and feel a total prat.
Our local Mercedes dealers know absolutely nothing about the MP or about leisure batteries.
Can one of you lovely MP owners help put me on the right track please!
 

Epigram

Active Member
You don’t say if you have a Marco Polo or a Horizon
I have attached photos from the online manual for the battery connection under the bonnet. However this is for jump starting the vehicle and does not charge the leisure battery.
If you have a Marco Polo use a hook up cable to connect the vehicle to the mains supply. This will charge the leisure battery once the main vehicle (starter) battery is charged. Alternatively you could take the vehicle for a run.
 

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enano

Member
The engine battery is under the right front seat (at least, it is on vans for right-hand driving countries, where the driver seats on the left side).
If it has been very deeply discharged I would suggest taking it out and charging it outside the car. Easier to spot if something is really wrong with it, and less damage if it leaks or even explodes.

According to the manual, the engine battery will be charged if the MP is connected to an AC plug, but only after the leisure battery is full and only if it is within some conservative voltage limits. That may take some time and may not work at all if the engine battery is starting to fail.

BTW: charging the leisure battery while driving is really slow, as the MP only connects the alternator during braking to increase mileage. A mechanic hinted that the alternator is also connected when you turn on the driving lights (and, at least on my van, it works). If you have a leisure battery so deeply discharged you cannot even use the power seats, just turn on the engine AND the driving lights - instant miracle.
 

PamJ

New Member
Thank you. Useful to know. We have had leisure battery issues from the start with charge not being held even after journeys e.g. not enough for roof to be lowered after 2 days light use (Summer).
It’s going in to be checked next week with dead /exploded leisure battery disconnected.
I will pass this information on.
 

Martin Sierink

New Member
We have a MP from 2017. After discharging the support /leisure battery as a result of standing still for a long time with a connected USB phone charger, we went driving. That's not a good idea. As soon as you go driving (start the enigine), the support battery and the start battery are switched parallel. The consequence of this is that if one of the batteries is deeply discharged (in our case the support battery) a high current will flow between the two batteries. In our case this high current caused the relay (which controls the parallel circuit) to melt. Luckily for us, this meant the power was cut.


Because the manual does not provide complete information, I will indicate below how it works in my opinion with an MP from 2017.

Discharge:
When the engine is off and the MP is not connected to an AC network, the central display shows the voltage of the support battery and the bar diagram has a left and a right bar. This left and right bar means that a current of less than 0.5A is being drawn from the support battery. As soon as you use for example the 12V connection next to the kitchen with more than 0.5A, the bar diagram shows the state of charge level of the support battery. More bars means further charged where one bar is 10%. Less than 6 bars actually means already deeply discharged.

Load:
If you connect the MP to an AC network, the central display shows the voltage of the support battery and the bars in the bar graph are running from left to right. The support battery is now charged and as soon as it is full, both batteries are maintained with a charging current. So in this case you cannot see the state of charge.

When you start the engine, both batteries are connected in parallel and the alternator starts charging them. At that time, the central display will show the charging voltage and the bar diagram either a left end right bar(less then 0,5A) or the state of charge.

With above information you can check the condition of the support battery both when stationary and while driving.

Finally, my advice in case one of the two batteries is deeply discharged to disconnect this battery to prevent melting of the relay or worse a fire due to a short circuit.
 

Epigram

Active Member
We have a MP from 2017. After discharging the support /leisure battery as a result of standing still for a long time with a connected USB phone charger, we went driving. That's not a good idea. As soon as you go driving (start the enigine), the support battery and the start battery are switched parallel. The consequence of this is that if one of the batteries is deeply discharged (in our case the support battery) a high current will flow between the two batteries. In our case this high current caused the relay (which controls the parallel circuit) to melt. Luckily for us, this meant the power was cut.


Because the manual does not provide complete information, I will indicate below how it works in my opinion with an MP from 2017.

Discharge:
When the engine is off and the MP is not connected to an AC network, the central display shows the voltage of the support battery and the bar diagram has a left and a right bar. This left and right bar means that a current of less than 0.5A is being drawn from the support battery. As soon as you use for example the 12V connection next to the kitchen with more than 0.5A, the bar diagram shows the state of charge level of the support battery. More bars means further charged where one bar is 10%. Less than 6 bars actually means already deeply discharged.

Load:
If you connect the MP to an AC network, the central display shows the voltage of the support battery and the bars in the bar graph are running from left to right. The support battery is now charged and as soon as it is full, both batteries are maintained with a charging current. So in this case you cannot see the state of charge.

When you start the engine, both batteries are connected in parallel and the alternator starts charging them. At that time, the central display will show the charging voltage and the bar diagram either a left end right bar(less then 0,5A) or the state of charge.

With above information you can check the condition of the support battery both when stationary and while driving.

Finally, my advice in case one of the two batteries is deeply discharged to disconnect this battery to prevent melting of the relay or worse a fire due to a short circuit.
Thanks for posting and printed off for reference.
It’s difficult to know what is going on without seeing a wiring diagram which Mercedes / Westfalia seem to keep to themselves . It would have been good practice to put a current limiting resistor or fuse in the circuit to protect the relay under this foreseeable circumstance.particularly if, as you say, the vehicle should not be started with a completely dead leisure battery.
 
Last edited:
Further battery issues. I have owned a Marco Polo for 5 years and have recently started to experience problems with the leisure battery losing charge. This culminated with it impacting on the main battery, resulting in a dead battery. Mercedes recovery came to the house and jump started the battery.
After a long run this is now fine. However I lost navigation and reversing camera in the process (although Mercedes maintain thats not their issue). Mercedes cannot explain why but are offering to try and resolve by a software update for £2,600+ vat! Mercedes have also checked the leisure battery and maintain that it is working fine. It isn't. Even after an extensive mains charge once disconnected the battery quickly loses charge. Now this is where I welcome your assistance. I'm about to go to a festival. So no hook up. The charge will quickly reduce below 10.5V so the pop up won't when leaving pop down. The manual refers to a button behind the cupboard under the burners. Now I cannot figure out how to get to it or find it so that I can manually lower the roof. Has anyone actually found this button or have any other bright idea as to how I get the roof down in these circumstances? Other than trying to find a 3 pin socket somewhere of course!
You plain English responses would be very much appreciated
Andrew
 

SteveR

Active Member
....The manual refers to a button behind the cupboard under the burners. Now I cannot figure out how to get to it or find it so that I can manually lower the roof. Has anyone actually found this button or have any other bright idea as to how I get the roof down in these circumstances? ...
The emergency button is in the cupboard under the gas burners as you say. Are you saying you don't have one?

Does this help or have you already seen....

Screenshot 2022-07-05 at 07.28.19.png
 

Epigram

Active Member
The button should be there but it is difficult to find. When I first had my MP I printed off the instructions that SteveR has posted above and left them under the cutlery tray. I also checked the emergency lowering procedure actually worked.
I would much prefer a manual roof. Less to go wrong. I have seen more durable connections to the microswitches on a toy car and the electric screw -jacks sound as though they could do with and oil and are waiting to pack up at the most inconvenient moment.
I hope you get your battery problems Openwaterswimmer
 

Sarahjane

Member
Further battery issues. I have owned a Marco Polo for 5 years and have recently started to experience problems with the leisure battery losing charge. This culminated with it impacting on the main battery, resulting in a dead battery. Mercedes recovery came to the house and jump started the battery.
After a long run this is now fine. However I lost navigation and reversing camera in the process (although Mercedes maintain thats not their issue). Mercedes cannot explain why but are offering to try and resolve by a software update for £2,600+ vat! Mercedes have also checked the leisure battery and maintain that it is working fine. It isn't. Even after an extensive mains charge once disconnected the battery quickly loses charge. Now this is where I welcome your assistance. I'm about to go to a festival. So no hook up. The charge will quickly reduce below 10.5V so the pop up won't when leaving pop down. The manual refers to a button behind the cupboard under the burners. Now I cannot figure out how to get to it or find it so that I can manually lower the roof. Has anyone actually found this button or have any other bright idea as to how I get the roof down in these circumstances? Other than trying to find a 3 pin socket somewhere of course!
You plain English responses would be very much appreciated
Andrew
Not sure if this helps but there is a YouTube “camping secrets” that has a series of MP tutorials one of which is about the pop up roof and shows where this button is.
 

ArturoFB

New Member
Not sure if this helps but there is a YouTube “camping secrets” that has a series of MP tutorials one of which is about the pop up roof and shows where this button is.
I have had many problems with the Marco Polo battery. I found myself on a rainy day with both batteries flat and all the windows and doors open. I had to wait for two hours until they came to rescue me. They replaced the batteries and the next day I had the same problem. I had to send the van into the garage to fix. But that was only the beginning of a long list of problems in which the worst one has been a fissure in the exhaust pipe
 
M

Marilyn

Member
VIP Member
Can anyone provide me with an idiots guide to MP batteries please.
We had a new leisure battery last year after the existing one exploded emitting smoke and gases while driving it, not a pleasant experience!
After another period of the MP standing still because of Covid restrictions etc went to charge the engine battery but now know I attached charger to the relay under the bonnet for a few hours, as I mistook it for the battery. Possibly linked to this the new leisure battery started to smoke and give off fumes the same as last time.
I can’t find where the engine battery is or it’s charging points and feel a total prat.
Our local Mercedes dealers know absolutely nothing about the MP or about leisure batteries.
Can one of you lovely MP owners help put me on the right track please!
The actual battery is under the drivers seat & thx leisure battery is under the passenger seat
 

Method7

Active Member
There is a power / battery point under the bonnet - thought I had a photo but can’t find it. If you face the car with the bonnet open on the left hand side there is a box that looks like it could be a battery cover but I think it’s a relay box bit it has a sliding red cover the you can push back and it exposes the positive post. The negative post is down a bit lower close to the inner wing, it may well be on the inner wing or engine mount. It’s sort of obviously shaped to accept a jump lead.
 
The leisure battery is too underpowered for kit on board. Also the new mbux system in ours showed an issue not getting above 90. That was seemingly fixed. Now I can get it above 60. Livid with mb as this is one of a dozen things gone wrong.
 
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